Crop improvements can help us to meet the challenge of feeding a population of 10 billion, but can we breed better varieties fast enough? Technologies such as genotyping, marker-assisted selection, high-throughput phenotyping, genome editing, genomic selection and de novo domestication could be galvanized by using speed breeding to enable plant breeders to keep pace with a changing environment and ever-increasing human population.

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Breeding crops to feed 10 billion.

International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)

The integration of new technologies into public plant breeding programs can make a powerful step change in agricultural productivity when aligned with principles of quantitative and Mendelian genetics. The breeder’s equation is the foundational application of quantitative genetics to crop improvement. Guided by the variables that describe response to selection, emerging breeding technologies can make a powerful step change in the effectiveness of public breeding programs. The most promising innovations for increasing the rate of genetic gain without greatly increasing program size appear to be related to reducing breeding cycle time, which is likely to require the implementation of parent selection on non-inbred progeny, rapid generation advance, and genomic selection. These are complex processes and will require breeding organizations to adopt a culture of continuous optimization and improvement. To enable this, research managers will need to consider and proactively manage the, accountability, strategy, and resource allocations of breeding teams. This must be combined with thoughtful management of elite genetic variation and a clear separation between the parental selection process and product development and advancement process. With an abundance of new technologies available, breeding teams need to evaluate carefully the impact of any new technology on selection intensity, selection accuracy, and breeding cycle length relative to its cost of deployment. Finally breeding data management systems need to be well designed to support selection decisions and novel approaches to accelerate breeding cycles need to be routinely evaluated and deployed.

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Enhancing the rate of genetic gain in public-sector plant breeding programs: lessons from the breeder’s equation

Integration of genomic technologies with breeding efforts have been used in recent years for chickpea improvement. Modern breeding along with low cost genotyping platforms have potential to further accelerate chickpea improvement efforts. The implementation of novel breeding technologies is expected to contribute substantial improvements in crop productivity. While conventional breeding methods have led to development of more than 200 improved chickpea varieties in the past, still there is ample scope to increase productivity. It is predicted that integration of modern genomic resources with conventional breeding efforts will help in the delivery of climate-resilient chickpea varieties in comparatively less time. Recent advances in genomics tools and technologies have facilitated the generation of large-scale sequencing and genotyping data sets in chickpea. Combined analysis of high-resolution phenotypic and genetic data is paving the way for identifying genes and biological pathways associated with breeding-related traits. Genomics technologies have been used to develop diagnostic markers for use in marker-assisted backcrossing programmes, which have yielded several molecular breeding products in chickpea. We anticipate that a sequence-based holistic breeding approach, including the integration of functional omics, parental selection, forward breeding and genome-wide selection, will bring a paradigm shift in development of superior chickpea varieties. There is a need to integrate the knowledge generated by modern genomics technologies with molecular breeding efforts to bridge the genome-to-phenome gap. Here, we review recent advances that have led to new possibilities for developing and screening breeding populations, and provide strategies for enhancing the selection efficiency and accelerating the rate of genetic gain in chickpea.

https://link.springer.com/content/pdf/10.1007/s00122-020-03584-2.pdf

Integrating genomics for chickpea improvement: Achievements and opportunities

A new plant breeding method-the biotron breeding system (BBS)-can rapidly produce advanced generations in rice (Oryza sativa L.) breeding. This method uses a growth chamber (biotron) with CO2 control, accompanied by tiller removal and embryo rescue to decrease the period before seed maturity. However, tiller removal and embryo rescue are laborious and impractical for large populations. We investigated the influences of increased CO2, tiller removal, and root restriction on the days to heading (DTH) from seeding in growth chambers. The higher CO2 concentration significantly decreased DTH, but tiller removal and root restriction had little effect on DTH and drastically reduced seed yield. Based on these findings, we propose a simplified BBS (the sBBS) that eliminates the need for tiller removal and embryo rescue, but controls CO2 levels and day-length and maintains an appropriate root volume. Using the sBBS, we could reduce the interval between generations in 'Nipponbare' to less than 3 months, without onerous manipulations. To demonstrate the feasibility of the sBBS, we used it to develop isogenic lines using 'Oborozuki' as the donor parent for the low-amylose allele Wx1-1 and 'Akidawara' as the recipient. We were able to perform four crossing cycles in a year.

https://www.jstage.jst.go.jp/article/jsbbs/66/4/66_15038/_pdf

A practical, rapid generation-advancement system for rice breeding using simplified biotron breeding system.

Sorghum [ Sorghum bicolor (L.) Moench] is a model C4 cereal for both basic and applied research. It has most of the traits of a model plant species: large embryos that are easy to rescue, moderate genome size of about 760 Mb, several unique traits not found in other species, plenty of seeds, and many important agronomic as well as commercial uses. However, it takes a long time to complete its breeding cycle. ther oproblems encountered during the research on sorghum breeding were early desiccation of embryos from mutants and wide hybridization, and the high-yielding cultivars and plants grown in controlled environments are usually uniculm, which limits their use in crossing to obtain both selfed and crossed seeds. The objective of this research was to find ways to obtain cross- and self-pollinated seeds from the same plant, con-serve the vital embryos, and most important, shorten the breeding cycle. Two methods are reported here. The first method was to produce crossed as well as selfed seeds on the same panicle of the usually uni-culm plant. The sec-ond method was to carry out embryo rescue to save vital embryos as well as shorten the breed -ing cycle from the regular 17 to 11 wk. By these two methods, the breeding cycle of sorghum was made comparable or even shorter than that of other model crops, which would allow the development of breeding materials much faster.G. Rizal, S. Karki, M. Alcasid, F. Montecillo, K. Acebron, N. Larazo, R. Garcia, and W.P. Quick, C4 Rice Center, International Rice Res. Institute, Los Banos, Laguna, DAPO Box 7777, Metro-Manila, Philip -pines; I.H. Slamet-Loedin, Plant Breeding, Genetics and Biotechnology Division, International Rice Research Institute, Los Banos, Laguna, DAPO Box 7777, Metro-Manila, Philippines; W.P. Quick, Dep. of Animal and Plant Sciences, Univ. of Sheffield, Sheffield, UK. G. Rizal, and S. Karki contributed equally. Received 19 July 2013. *Correspond -ing author (w.p.quick@irri.org).

Shortening the Breeding Cycle of Sorghum, a Model Crop for Research

An efficient method for crossing green foxtail (Setaria viridis) is currently lacking. S. viridis is considered to be the new model plant for the study of C4 system in monocots and so an effective crossing protocol is urgently needed. S. viridis is a small grass with C4-NADP (ME) type of photosynthesis and has the advantage of having small genome of about 515 Mb, small plant stature, short life cycle, multiple tillers, and profuse seed set, and hence is an ideal model species for research. The objectives of this project were to develop efficient methods of emasculation and pollination, and to speed up generation advancement. We assessed the response of S. viridis flowers to hot water treatment (48°C) and to different concentrations of gibberellic acid, abscisic acid, maleic hydrazide (MH), and kinetin. We found that 500 μM of MH was effective in the emasculation of S. viridis, whilst still retaining the receptivity of the stigma to pollination. We also report effective ways to accelerate the breeding cycle of S. viridis for research through the germination of mature as well as immature seeds in optimized culture media. We believe these findings will be of great interest to researchers using Setaria.

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Michael Alcasid

Papers

Shortening the Breeding Cycle of Sorghum, a Model Crop for Research

The Use of Maleic Hydrazide for Effective Hybridization of Setaria viridis